In general, when producing a pneumatic tire, a tire mold which is constituted with a split mold is used. The mold is attached to a vulcanization machine (a press machine) after assembled at room temperature.
FIG. 5 is a sectional view illustrating a conventional tire mold, and FIG. 6 is a top view illustrating a fully closed state of the tire mold. Each of them illustrates a state after assembled.
As illustrated in FIG. 5, the tire mold 41 is constituted by arranging a pair of upper and lower side plates 51 and 52, a sector 53, a sector shoe 54 holding the sector 53, and an actuator 55, in sequence from an inner side to an outer side in a radial direction of the tire. And, 57 is a lower mold plate supporting the lower side plate 52, and 56 is an upper mold plate supporting the upper side plate 51.
In FIG. 5, an upper mold is constituted with the sector 53, the sector shoe 54, the actuator 55, the upper side plate 51, and the upper mold plate 56, and a lower mold is constituted with the lower side plate 52 and the lower mold plate 57.
At the time when the tire mold 41 assembled is fully closed, a position of the sector 53 against one pair of upper and lower side plates 51 and 52 is regulated when each of projection parts 53a and 53b formed in the upper and lower sides of the sector 53 contacts respectively each of outer diameter portions 51a and 52a of the side plates 51 and 52. And when the actuator 55 moves up and down, the sector 53 attached to the sector shoe 54 slides inwardly and inwardly along the tire radial direction.
Thus, although the moving range of the sector shoe 54 is regulated against actuator 55, a fixed play is provided in a tire peripheral direction and a tire radial direction at each sector shoe 54, as illustrated in FIG. 6, in order to make smooth sliding of the sector shoe 54 toward the tire diameter direction.
Since assembling of the tire mold 41 is performed at room temperature as described above, a clearance S is formed in a tire peripheral direction at each of sectors 53 made from aluminum in consideration of the thermal expansion by vulcanization temperature.
Accordingly, in an assembling stage of the tire mold 41, positions in peripheral direction of the sector shoe 54 and the sector 53 attached to the sector shoe 54 are not regulated.
And, although an entering margin of the sector 53 to a diameter direction is regulated when the sector 53 contacts side plates 51 and 52, the accuracy which regulates the position of sector 53 against side plates 51 and 52 becomes low in conjunction with the play of the above-mentioned peripheral direction, since an inner diameter of sector 53 is larger than an outer diameter of side plates 51 and 52 at the time of the assembling at room temperature. As a result, in an assembling stage of the conventional tire mold 41, the core of the upper mold against the lower mold is deviated to a small extent, the clearance S between sectors 53 is unevenly distributed, and the tire mold 41 is attached so that the upper mold inclines against the lower mold.
Therefore, conventionally, in assembling of the tire mold 41, the assembling has been performed by inserting a jig (an illustration is omitted) into a play between the sector shoe 54 and the sector 53 or a clearance S between sectors 53 themselves.
However, work load becomes large when such an insertion jig is used.
In the conventional mold, since the pressurization at a time of press was received by contacting the sector and side plate made from aluminum in a tire diameter direction and by contacting the sides themselves of the sectors in a tire peripheral direction, an inner periphery and a side of the sector wore out with the use of the mold, and therefore, correspondence to these problems were inevitable.
For such a problem, an art which prevents wear of sectors by contacting mutual sides of the sector shoes is disclosed in Patent Document 1. By deleting a clearance in the tire radial direction of the sector shoe, the effect of suppressing a deviation of the upper and lower molds is expected. However, since an entering margin to the tire radial direction of a sector shoe becomes fixed, a phenomenon happens in which the sector cannot be closed depending on a mold.
In Patent Document 2, an art is disclosed which controls a deviation of upper and lower molds by contriving the shapes of the bottom of a sector shoe and the upper surface of a lower mold container contacting thereto. However, wear of the sector cannot be prevented by the art.